Texas Instruments TMS320DM648 manual Video Display Counters

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Video Display Mode Selection

Frame

Figure 4-4. Progressive Blanking Intervals and Video Area

	Field 1 Vertical Blanking
		Field 1 Image Vertical Offset
		Field 1 Active Video
Horizontal Blanking	Image Horizontal Offset	Field 1 Image Height
	Field 1	Field 1 Image Width

Field 1

4.1.2 Video Display Counters

To generate the image timing, the video display module uses five counters:

∙Frame line counter (FLCOUNT)

∙Frame pixel counter (FPCOUNT)

∙Image line counter (ILCOUNT)

∙Image pixel counter (IPCOUNT)

∙Video clock counter (VCCOUNT)

The frame line counter (FLCOUNT) counts the total number of lines per frame including vertical blanking intervals. The frame pixel counter (FPCOUNT) counts the total number of pixels per line including horizontal blanking intervals. FLCOUNT begins counting at the start of the vertical blanking interval of the first field. FPCOUNT begins counting at the end of the horizontal blanking interval of each line. They are reset when they reach their stop values as specified in the video display frame size register (VDFRMSZ).

The image line counter (ILCOUNT) and the image pixel counter (IPCOUNT) track the visible image within the field. ILCOUNT begins counting at the first display image line in each field. IPCOUNT begins counting at the first displayed image pixel on each line. They stop counting when they reach the image height and image width as specified in the video display field n image size register (VDIMGSZn).

The video clock counter (VCCOUNT) counts VCLKIN transitions to determine when to increment FPCOUNT and IPCOUNT as determined by the video display mode. In Y/C mode, FPCOUNT and IPCOUNT increment on each VCLKIN rising edge. In BT.656 mode, FPCOUNT and IPCOUNT increment on every other VCLKIN rising edge. In raw mode, FPCOUNT and IPCOUNT increment on every 1 to 16 VCLKIN cycles as programmed by the INCPIX bits in the video display threshold register (VDTHRLD).

FPCOUNT and FLCOUNT are compared to various values to determine when to assert and negate various control signals. The 12-bit FPCOUNT is used to determine where to enable and disable horizontal sync and blanking information along each scan line. The state of FPCOUNT is reflected in the VDXPOS bits of the video display status register (VDSTAT).

96 Video Display Port SPRUEM1 –May 2007

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